Naphtha reforming process



Feb- 23 1954 R. w. Knees Erm.

NAPHTH REFORMING PROCESS Filed May 1, 1951 62E-ugh un Clbborrze Patented Feb. 23, 1954 T OFFICE NAPHTHA REFORMING PROCESS Robert W. Krebs and Alexis Voorhies, Jr., Baton Rouge, La., assignors to Standard Oil Development` Company, a corporation of Delaware Application May 1, 1951, Serial N o. 223,996

12 Claims.

The present invention pertains to naphtha improvement and more particularly to the catalytic reforming of hydrocarbon fractions boiling within the motor fuel boiling range to convert' said hydrocarbon fractions into motor fuels of improved anti-knock quality. Specically, this invention pertains to the upgrading of petroleum naphthas by treating the same with certain gaseous olens in the presence of hydrogen transfer catalysts under conditions which Will convert the naphthenes to aromatics and then combining the reformed naphtha with a residual stock in a high temperature fludized coking zone wherein the residual stock is converted to more valuable lower boiling products.

Numerous processes have been proposed for the conversion or. reforming of hydrocarbon fractions boiling within the motor fuel or naphtha range to increase the aromaticity and improve the anti-knock characteristics of said hydrocarbon fractions. Reforming processes employing catalysts. especially hydroforming and aromatizing are widely used in the petroleum industry to upgrade or improve the anti-knock characteristics of motor fuels. It has also been proposed to subject naphthenic petroleum fractions' to hydrogen transfer with liquid olenic hydrocarbons whereby the naphthenic constituents are converted to aromatics and the olenic hydrocarbons are converted to paraffnic hydrocarbons by the hydrogen' removed from the naphthenic constituents. It has also been proposed to convert residual stocks into lower boiling or motor fuel components by a coking operation utilizing the fluidized solids technique with steam or naphtha as a iluidizing agent. In View of the increasing demands for greater volumes of motor fuel 'of improved anti-knock properties, these processes have been the subject of intensive investigation in an eort to find new catalysts or new conditions or techniques for carrying out the y`coking of residual stock and the reforming or upgrading of motor fuel or naphtha fractions to increase yields and/or improve the anti-knock characteristics of the motor fuel product.

It is the object of this invention to provide an improved process for catalytically reforming hydrocarbon fractions boiling within the motor fuel boiling range to form motor fuels of higher anti-knock ratings in high yields.

It is also the object of this invention to prepare motor fuels of good anti-knock properties and in good yields by reforming a naphtha underhy- Itis a further object of this invention to subject a naphtha fraction to hydrogen transfer conditions in the presence of the Cz, C3 and C4 gases formed in the fluid coking of residual stocks at high temperatures and then to combine the resultant treated naphtha with the residual stock in the high temperature fluid coking zone.

These and other objects Will appear more clearly from the detailed specification and claims which follow.

In accordance with the present invention a residual stock or a hydrogen deficient residual or cycle stock such as a topped or reduced crude is coked on uidized, catalytically inert solids such as sand petroleum coke, pumice or the like at the high temperature fluid coking operation.

The pretreated naphtha serves as a fluidizing medium replacing or supplementing steam or other conventional fluidizing gas and exerts a synergistic effect upon the coking of the residual stock, giving less byproduct formation and higher yields of products of improved properties.

Reference is made to the accompanying drawing illustrating diagrammatically one embodiment of the present invention.

In the drawing, IIJ is a coking vessel similar to conventional dense bed, bottom drawoff fiudized solids contacting vessels. I I is a transfer line for the introduction of finely divided solids in admixture with fluidizing gas or vapors. The transfer line II discharges into a suitable distributing inlet chamber I2 comprising an inverted conical member superposed by a perforated grid member I3 which serves to distribute the lincoming solids andY vapors uniformly over theentire cross section of the coking vessel I 0. The coking vessel is charged with finely divided substantially inert solids such as sand, pumice, coke, clay, etc., having a particle size of about 30-400 mesh which are maintained' as a dense, uidized, turbulent bed I4 having a denite'level I5 or interface separating the turbulent bed or dense phase I4 from an upper dilute or disperse phase I6. Linear supercial gas velocities through the coking vessel may be varied between about 0.3 to about 5.0 ft. per second to establish apparent densities of about 20 to 60 lbs. per cu. ft. in dense bed I4 and about 0.001 to 0.1 lb. per cu. ft, in disperse phase I6.

A line I 1 is provided for supplying residual stock for coking to the coking vessel ID. The line I1 connects to suitable spray nozzles mounted on manifold I8 arranged in the disperse phase I 6 in the upper part of coking vessel I0. The distance of travel of the droplets` of residuum through the disperse phase, i. e. before contacting the main body of fluidized solids should be about 5 to 20 feet, preferably about l0 feet. Design of the coking vessel and the fluidizing conditions maintained therein should be suchas` Will permit a residence time of the upflowing vapors in the dense bed I4 of about 3 120,60 seconds and descending time of-` liquid` residuum through the disperse phase I6 of about 0.5 to 10 seconds depending upon the degreev of dispersion of the spray and the velocity of upflowing gases. The liquid residuum feed rate may be about 0.3 to 5.0 wt./hr./wt. (lbs., of residuum p er hour per lb. ofV solid contact material in the coking vessel). The temperature within the dense bed :I4 should be maintained at about 1050-l150 F. by circulation of the contact-solids as will now be described.

Contact solids from the dense bed I4 pass downwardly around inletchamber I2 at the bottom of the coking vessel IIJ to an outlet pipe 20. Stripping gas, preferably steam, is introduced into the lower part of the coking vessel to minimize the amount of hydrocarbon entrained or adsorbed on the solids leaving the coker vessel. Part of the coke-carrying solids passing into outlet pipe 20 may be withdrawn from the system through valve controlled dis.- charge line 2|. The remainder of the contact solids pass dovvnv through conduit 20 in fluidized state. A stream of steam or other stripping or fluidizing gas is supplied through one or more taps 22 on conduit 20, uidizing the. solid particles and removing further amounts of Vaporizable material from the contact solids before admixture. of said solids With air or combustion gas.

The stripped contact solids are discharged. from conduit 20 through control valve 23 intov transfer line 24 Where they are. picked up by a stream of air or combustion gas and conveyed to heater vessel. 25. The transfer line 24- discharges the suspension of contact solids and air into inlet chamber 2E arranged adjacent the bottom of heater vessel 25; The inlet chamber comprises an inverted conical section superposed by a horizontally disposed perforated. plate. or grid 2 which serves. to distribute the incoming solids and air uniformlyover the entire cross section of the heater vessel 25. The linear superficial velocity of the air passing through the heat ing vessel 25 similarly to the gas velocities through coking vessel Il] may be varied between about 0.3 to about 5.0 ft. per second and forms therein a dense', fluidized, turbulent bed 28' of contact solids having a definite level 29 or' interface separating it from the dilute or' disperse The combustion gases pass. tothe atmosphere via stack 32 or, if. desired to. heat recovery equipment and, then. to the atv kburning rates and to achieve good utilization of the air supplied to the heater vessel, The solids leaving the coking vessel will ordinarily have a coke content that is about 0.5 to about l0 wt. per cent higher than that of the solids leaving the heater vessel. This figure depends upon the amount of coke deposited by the partisular feed used and the ratio of solids circulation rate to oil feed rate. Fluidized solid con-r tact material carrying about 5 to 100 wt. per cent of coke may be Withdrawn from the coking vessel for circulation to the heater vessel 25 at a rate of about 1 to 20v times the total oil'feedj rate to the coking vessel. withdrawn contact material in air passes through the transfer line 24 and distributor plate 2li to form a` dense rluidizedbed in which the desired amount of coke is burned off ofthe contactv particles. As a result of the combustion of the coke taking place in the transfer line and heater vessel 25, the solid contact materials are heated' to temperatures of about 1'150' to 1300"v F; Ordi#-v narily the temperature of the dense bed of`con.

tact material in heater 25 should beat least about 50 F. higher than the temperature of" the dense uidized bed I4 in coking vessel Ill. About i000 to 6000 cu. ft. of air per barrel of total feed to the ooking vessel Will suffice to burn off` all the cokeV formed and maintainy the system` in heat balance at the conditions specified.

Fluidized solid contact material at the temperature of the dense bed 28 is Withdrawn through standpipe 33 connectedv to the bottom ofr the. heater vessel 25. The solid contact materials are aerated and/or stripped with steam or inert gas supplied through. one or more taps 3.4'.Y The. reheated contact particles are discharged through control valve 35 into4 transfer line II where they are picked up by. aY stream of naphtha which is given a pretreatment as. Willv beV described. ini-.- mediately below,y and conveyed' throughA line II to coking vessel I0. at. substantiallyv the same. rate at. whichv they Were WithdrawnY therefrom., so as, to supply,v heat required in coking vessel. Ill assensible heat. of the reheated contact. solids..

In order to facilitate the coking.. of theresiduum..

and toy provide vapors for fluidization of ther dense bed of contact solids in coking vessel, I0,i a naphtha feed. stock is. used after suitabley pre.- treatment., The naphtha feed stoclfglvvhich` may be. a virgin. naphtha a catalytically cracked naphtha, or the. like havingV a. boilingv range be,.

tween aboutv and 430? F., is supplied through.

inlet line. 38 and'. is contacted with a. hydrogen. transfer catalyst in admixture with the C2., Ca and C4 fractionfrom the Coker crackedproducts ina fixed. bed, moving bed. fluidized bed or sus-- pensoid type operation. Suitable7 hydrogen` transfer catalysts. include activated carbon,

vanadium oxide on alumina, alumina on silicaIl molybdenum oxide on alumina or the like.

Insome installations, activated carbon` catalyst.

may.v beadded directly tdthenaphtha and-passed.

alongI Withit. directly intothe coking zone withJ out adversely affecting the subsequent..ook-ills#` The suspension of' afemsaa operation. 11n the embodiment vof the invention shown on the drawing the hydrogen transfer cat--v alyst is contained in two fixed bed reactors 52 and 62 wherein the naphtha is treated. Only-one of the reaction vessels is used at a time. For example,.the heated naphtha may be introduced through line 43 into line 5| and the reactor 52, out through line 53 and 54 to line ll.v Meanwhile the alternate reactor 62 is being regenerated or freed from carbonacecus deposits by the introduction of air or other combustion gas from line 55 through line 66 and out through lines 6l and 58. When the catalyst in vessel 52 becomes fouled, the valving of the two vessels is reversed.

vIn accordance with this invention there is also added tothenaphtha feed prior to the pretreatment, the highly olefinic cracked gases or C2.. C3 and C4 fraction from the coker cracked products. These cracked gases are taken overhead from the fractionator 45 through line 40. and are intermixed with the naphtha-catalyst mixture and the resultant mixture is heated to the desired reaction temperature of about 800 to about 1000 F. as by passage in indirect heat exchange with the reaction products from coker vessel I and/or by passage through line 4l through heater coils 42 arranged in the dense, iluidized bed 28 in heater 25. The feed rate of naphtha and the size of vessels 52 and 62 are so adjusted as to give a space velocity of 0.2 to 2.0 volumes of naphtha per volurne of catalyst per hour to obtain the desired conversion of the naphtha. If desired, elevated pressures of about 20G-1000 lbs. per sq. in. may be applied in coils 42 and vessels 52 or.62. The naphtha passing through line Il serves to pick up and convey the reheated contact solid particles baci: into the coking lvessel l0. If necessary, or desired, steam or other uidizing gas may also be supplied to line Il through inlet line 44.

Vaporous coking products containing small amounts of entrained solid particles pass into the disperse phase I6 in the upper part of coker vessel I0 and pass therethrough countercurrently to descending droplets of residuum feed. In this way the said feed droplets are preheated and pretreated to give off relatively low temperature coking products. Simultaneously the vaporous coking products are quenched to temperatures approximating or somewhat above the temperature of the residuum feed thereby avoiding excessive cracking. At the same time most of the solid particles entrained with the vaporous coking products are scrubbed out so that no special gas solids separation equipment 0r cyclones are required at the vapor outlet of the coking vessel.

The vaporous coking products amounting to about 80-95 wt. per cent on total feed pass overhead from coking vessel l0 through line 45 at temperatures of about '700-1000 F. into fractionating column 46. About 10-25 wt. per cent of product gases based on total feed are taken overhead from fractionator 46 through line 40 for admixture with the feed naphtha as described above. If desired, part of the cracked gases may be withdrawn from the unit and passed to suitable processing or recovery equipment.

-Coker cracked naphtha boiling up to about 430 F. amounting to about 50-80 vol. per cent based on total feed is recovered through line -41 and passed to gasoline storage or blending. Coker gas oil boiling within the range of about 430-950" F. and amounting to to 20 vol. per cent of the total feed is Withdrawn from fractionator 46 through line 48 and may be blended with virgin gas oil and passed to a catalytic cracking operation'. Coker bottoms boiling above 'about 950 F. and'amounting to about 1 5 vol. per cent of the..

total feed is Withdrawn through line 49 and passed to fuel oil storage,'or the like or, if desired,` it may be recycled to the coking vessel for retreatment therein.

An example of a typical embodiment of this invention is as follows:

Example In a plant handling 10,000 B./D. of a 10 API pitch,\the pitch feed isA preheated to 750 F. and fed into a fluid coking reactor over fluidized coke particles in the range of 20 to 200 mesh size at a weight space velocity of one weight of feed per hour per weight of solids in the reactor vessel. The coking takes place at 1100 F. in which the pitch is converted largely to distillate fuels, coke and. gas. The coke formation is 15 per cent on feed. The fluidized solids are circulated between a burner vessel and the reactor at a solids-topitch `ratio of about yten to one. In the burner,

about four per cent on feed of carbon is burned 01T to supply heat for the process and about eleven per cent must be drawn off. The amount burned. representing about one-tenth per cent of the circulating stream, increases the temperature of the solids stream to about 1200 F. About 20 weight per cent ofthe pitch is converted to light gases which are fed along with 10,000 B./D. of extraneous virgin naphtha to vessels containing a hydrogen transfer catalyst in the form of pills or granules. The naphtha is fed at a volumetric space velocity of 0.5 v./v./hr. and the catalyst bed is maintained at an average temperature of around 900 F. Pelleted catalyst containing `10 per cent vanadium oxide on alumina is used as the catalyst. In this reactor, a large share of the naphthenes in the naphtha (which may amount to 10-20 volume per cent of the naphtha) are converted to aromatics and the olefms and the gases become saturated. The treated naphtha is then conducted to the injector at the base of the burner solids standpipe and serves as carrying gas for conducting that material to the coker reactor. All of the reactions described are conducted at substantially atmospheric pressure.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood that numerous variations are possible Without departing from the scope of the following claims.

What is claimed is:

1. A process for naphtha improvement which comprises pretreating a naphtha with olefinic cracked gases in contact with a hydrogen transfer catalyst under hydrogen transfer conditions, passing the treated naphtha in admixture with finely divided hot inert contact solids into a coking zone where the inert contactsolids are maintained as a dense fluidized bed having a level, spraying a residuum into the coking zone above said dense bed and converting the residuum to volatile products and coke, recovering olenic cracked gases from the vaporous reaction products and recycling the recovered olenic cracked gases to said naphtha pretreating step.

2. A process for naphtha improvement which comprises pretreating a 13G-430 F. naphtha with oleflnic cracked gases in contact with a hydrogen transfer catalyst under hydrogen transfer conditions, passing the treated naphtha in admixture with finely divided inert contact solids at a temwherein the inert contact solids are maintained 7 as a dense fluidized bed having Va level; introduc-` ingf'a petroleum residuum inthe `form of: dronletsv into said coking zone above said dense hed', maintaining the droplets in the coking'zone at temperatures of between 1050 and1150 F. for a period suicient to convert the residuum into volatile products and coke, recovering olenic cracked gases from the vaporous reactionvprod@ ucts and recycling the recovered olenic cracked gases to said naphtha pretreating step.

3; A process'for naphthaimprovement which comprises rpretreating a 13G-430 F. naphthawith.

olefinic cracked gases in contact With'a hydrogen transfer catalyst under hydrogen transfer conditions, passing the treated'naphtha in admixture withiinely divided inert contact solidsat a tem-- perature of' 1150-1300 F. into a coking zone wherein the'inert contact' solids are maintainedr as 'a-'densefiuidized bed having a level, introducingpa petroleum residuum in the form `of dropletsl into said coking zone above said dense bed, maine taining the droplets in the coking zone at tem-- peratures of between 1050 and 1150 F; for a peri-V odsuilicient to convert the residuum into volatileproducts and coke, recovering olefnic crackedf gases from the vaporous reaction products, re-

cycling the` recovered olenc cracked gases tosaid naphtha pretreating step, withdrawing al stream of contact solids directly from thedense bed in the coking zone, transferring the withdrawn contact solids to a heater vessel, burning carbonaceous deposits from said contact solids to heat the same to 1150-1300 F. recycling said heated solids to said coking zone.

4. The process as defined in claim 1 wherein the hydrogen transfer catalyst is activated carbon.

5.- The process as defined in claim 2 wherein thefhydrogen` transfer catalyst: is activated car:-

6. The. process as' dened in claim 3 wherein the: hydrogen transfer catalyst isactivated carbon.

7. The process as defined in claim 1 wherein the hydrogen .transfer catalyst is vanadium oxide on alumina.

8..'1`heprocess as defined in claimY 2 wherein the-hydrogen'. transfer catalyst is vanadium ox-v ide -on alumina.

9. The process as defined in claim 3 wherein.

the. hydrogen transfer catalystis vanadium ci@ ide' on alumina.

10. The processasdened in claim 1 wherein the. hydrogen transfer catalyst 'is molybdenum;

oxide. on alumina.

11. The process as defined' in claim 2 wherein:

the hydrogen transfer catalystA is molybdenum oxide ori-alumina.

12. Thezprocess as defined in claim wherein:

the hydrogen transfer catalyst is molybdenum oxideon alumina.

ROBERT W. KREBS'. ALEXIS VOORHIES, JR.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR NAPHTHA IMPROVEMENT WHICH COMPRISES PREHEATING A NAPHTHA WITH OLFFINIC CRACKED GASES IN CONTACT WITH A HYDROGEN TRANSFER CATALYST UNDER HYDROGEN TRANSFER CONDITIONS, PASSING THE TREATED NAPHTHA IN ADMIXTURE WITH FINELY DIVIDED HOT INERT CONTACT SOLIDS INTO A COKING ZONE WHERE THE INERT CONTACT SOLID ARE MAINTAINED AS A DENSE FLUIDIZED BED HAVING A LEVEL, SPRAYING A RESIDUUM INTO THE COKING ZONE ABOVE SAID DENSE BED AND CONVERTING THE REDISUUM TO VOLATILE PRODUCTS AND COKE, RECOVERING OLEFINIC CRACKED GASES FROM THE VAPOROUS REACTION PRODUCTS AND RECYCLING THE RECOVERED OLEFINIC CRACKED GASES TO SAID NAPHTHA PRETREATING STEP. 